Sphere-Shaped Lost Circulation Material (LCM) Having Straight Protrusions

ABSTRACT

A lost circulation material (LCM) that includes spheres having radially distributed and substantially-straight protrusions to facilitate engagement (such as interlocking and entanglement) of the spheres is provided. Each sphere has a plurality of protrusions to contact protrusions of adjacent spheres. The spheres may form plugs in channels, fractures, and other openings in a lost circulation zone. Additionally or alternatively, the spheres may form a bridge on which other LCMs may accumulate to seal openings in a lost circulation zone. Methods of preventing lost circulation using the spheres are also provided.

BACKGROUND Field of the Disclosure

The present disclosure generally relates to controlling lost circulationin a wellbore during drilling with a drilling fluid. More specifically,embodiments of the disclosure relate to a lost circulation material(LCM).

Description of the Related Art

Lost circulation can be encountered during any stage of operations andoccurs when drilling fluid (such as drilling mud) pumped into a wellreturns partially or does not return to the surface. While some fluidloss is expected, excessive fluid loss is not desirable from a safety,an economical, or an environmental point of view. Lost circulation isassociated with problems with well control, borehole instability, pipesticking, unsuccessful production tests, poor hydrocarbon productionafter well completion, and formation damage due to plugging of pores andpore throats by mud particles. In extreme cases, lost circulationproblems may force abandonment of a well.

Lost circulation can occur in various formations, such as naturallyfractured formations, cavernous formations, and highly permeableformations (for example, “super-K” formations having a permeabilitygreater than 500 millidarcy). Lost circulation can be categorized by theamount of fluid or mud lost as seepage type, moderate type, severe type,and total loss. The extent of the fluid loss and the ability to controlthe lost circulation with an LCM depends on the type of formation inwhich the lost circulation occurs.

SUMMARY

Lost circulation materials (LCMs), also referred to as loss controlmaterials are used to mitigate the lost circulation by blocking the pathof the drilling fluid (such as drilling mud) into the formation. Manyexisting LCMs include naturally-occurring or shaped materials that mayhave spherical, fibrous, or flaky shapes to block fractures, channels,and other openings in lost circulation zones. However,naturally-occurring or shaped materials may not have the optimal shapesfor forming bridges or plugs in fractures, channels, and other openingsin lost circulation zones to achieve a desired lost circulationperformance.

Additionally, naturally-occurring or shaped materials may also sufferfrom insufficient mechanical strength, chemical resistance, thermalstability, and biological degradation. Consequently, existing LCMsformed from naturally-occurring or shaped materials may perform poorlyat downhole conditions and may not seal and block lost circulation zonesfor sufficient time periods.

Many naturally-occurring or shaped LCMs swell in exposure to liquids ina well. However, swellable LCMs may have various problems, including arisk of premature swelling which could plug a bottom hole assembly(BHA), drill pipe, or both. Swellable LCMs may also have a risk of lateswelling such that an LCM is ineffective and does not swell in the lostcirculation zone and is swept away before use.

Embodiments of the disclosure are directed to an LCM having a pluralityof spheres such that each sphere has a plurality of radially distributedand substantially-straight protrusions to facilitate engagement (such asinterlocking and entanglement) of the spheres. Advantageously, thespheres do not rely on swelling to form plugs or bridges in a lostcirculation zone. The spheres may form improved and more effective plugsas compared to natural LCM products. Further, the spheres may formbridges in the lost circulation zone to enable the accumulation of anadditional LCM for improved sealing of the lost circulation zone.

In one embodiment, a method to control lost circulation in a lostcirculation zone in a wellbore is provided. The method includesintroducing an altered carrier fluid into the wellbore such that thealtered carrier fluid contacts the lost circulation zone, such that thealtered carrier fluid includes a carrier fluid and a lost circulationmaterial (LCM). The LCM includes a plurality of spheres. Each sphereincludes a sphere body and a plurality of substantially-straightprotrusions, each protrusion extending outward from a surface of thesphere body. A first protrusion of a sphere of the plurality of spheresis configured to contact a second protrusion of an adjacent sphere suchthat the plurality of spheres form a structure.

In some embodiments, the LCM consists of the plurality of spheres. Insome embodiments, the carrier fluid is an oil-based drilling mud or awater-based drilling mud. In some embodiments, the LCM is a first LCMand the method includes introducing an altered drilling fluid into thewellbore so that the altered drilling fluid contacts the lostcirculation zone, such that the altered drilling fluid includes adrilling fluid and a second LCM, such that the second LCM accumulates onthe structure. In some embodiments, each sphere of the plurality ofspheres has a diameter in the range of 5 millimeter to 38 mm. In someembodiments, the sphere body has a diameter in the range of 3millimeters to 34 mm. In some embodiments, each protrusion of theplurality of substantially-straight protrusions is separated from anadjacent protrusion by a radial distance in the range of 10° to 45°. Insome embodiments, each protrusion of the plurality ofsubstantially-straight protrusions has a length and the sphere body hasa diameter, such that the ratio of the length to the diameter is in therange of 0.1 to 3.5. In some embodiments, introducing the alteredcarrier fluid into the wellbore includes pumping the altered carrierfluid through a drill bit. In some embodiments, introducing the alteredcarrier fluid into the wellbore includes using a bypass system. In someembodiments, introducing the altered carrier fluid into the wellboreincludes introducing the altered carrier fluid into the wellbore usingan open-ended drill pipe.

In another embodiment, a lost circulation material (LCM) composition isprovided. The LCM composition includes a plurality of spheres. Eachsphere includes a sphere body and a plurality of substantially-straightprotrusions, each protrusion extending outward from a surface of thesphere body. A first protrusion of a sphere of the plurality of spheresis configured to contact a second protrusion of an adjacent sphere suchthat the plurality of spheres form a structure.

In some embodiments, each sphere of the plurality of spheres has adiameter in the range of 5 millimeter to 38 mm. In some embodiments, thesphere body has a diameter in the range of 3 millimeters to 34 mm. Insome embodiments, each protrusion of the plurality ofsubstantially-straight protrusions is separated from an adjacentprotrusion by a radial distance in the range of 10° to 45°. In someembodiments, each protrusion of the plurality of substantially-straightprotrusions has a length and the sphere body has a diameter, such thatthe ratio of the length to the diameter is in the range of 0.1 to 3.5.

In another embodiment, an altered drilling fluid is provided. Thealtered drilling fluid includes a drilling fluid and a plurality ofspheres. Each sphere includes a sphere body and a plurality ofsubstantially-straight protrusions, each protrusion extending outwardfrom a surface of the sphere body. A first protrusion of a sphere of theplurality of spheres is configured to contact a second protrusion of anadjacent sphere such that the plurality of spheres form a structure.

In some embodiments, each sphere of the plurality of spheres has adiameter in the range of 5 millimeter to 38 mm. In some embodiments, thesphere body has a diameter in the range of 3 millimeters to 34 mm. Insome embodiments, each protrusion of the plurality ofsubstantially-straight protrusions is separated from an adjacentprotrusion by a radial distance in the range of 10° to 45°. In someembodiments, each protrusion of the plurality of substantially-straightprotrusions has a length and the sphere body has a diameter, such thatthe ratio of the length to the diameter is in the range of 0.1 to 3.5.In some embodiments, the drilling fluid includes an oil-based drillingmud or a water-based drilling mud.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a 2-D schematic diagram of a sphere havingsubstantially-straight protrusions for a lost circulation material inaccordance with an embodiment of the present disclosure;

FIG. 2 is a 2-D schematic diagram of a structure (for example, a bridgeof plug) formed by the spheres of FIG. 1 via contact between theprotrusions in accordance with an embodiment of the disclosure; and

FIG. 3 is a block diagram of a process for the use of a protrusionsphere lost circulation material (LCM) in accordance with an embodimentof the disclosure.

DETAILED DESCRIPTION

The present disclosure will be described more fully with reference tothe accompanying drawings, which illustrate embodiments of thedisclosure. This disclosure may, however, be embodied in many differentforms and should not be construed as limited to the illustratedembodiments. Rather, these embodiments are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of the disclosure to those skilled in the art.

Embodiments of the disclosure include a lost circulation material (LCM)that includes spheres having radially distributed andsubstantially-straight protrusions to facilitate engagement (such asinterlocking and entanglement) of the spheres to create a flow barrierin a lost circulation zone. The LCM may be referred in the disclosure toas a “protrusion sphere LCM.” In some embodiments, the spheres may formplugs in channels, fractures, gaps, and other openings in a lostcirculation zone. In some embodiments, the spheres may form a bridge onwhich other LCMs may accumulate to seal or plug channels, fractures,gaps, and other openings in a lost circulation zone. In someembodiments, the protrusion sphere LCM may be used to preventseepage-type lost circulation (for example, lost circulation zoneshaving openings of less than 1 millimeter (mm) in size) to severe-typelost circulation (for example, lost circulation zones having openings upto 114 mm in size).

FIG. 1 is a two-dimensional (2-D) schematic diagram of a sphere 100having a sphere body 102 and radially distributed substantially-straightprotrusions 104 extending from the surface 106 of the body 102 inaccordance with an embodiment of the present disclosure. As shown inFIG. 1, the protrusions 104 may be distributed in equally spaced radialdirections (that is, in all directions) around the circumference of thesphere body 102. The sphere body 102 may have a diameter 108 in therange of 3 millimeters (mm) to 34 mm. The diameter of the sphere 100with the radially distributed protrusions 104 may be in the range of 5mm to 38 mm.

Each protrusion 104 protrudes from the surface 106 of the sphere 100 andis substantially-straight. As used herein, the termsubstantially-straight refers to a degree of curvature of less than 10°.Each protrusion 104 may have a length 110 in the range of 4 mm to 10 mm.

The protrusions 104 are distributed radially around the circumference ofthe sphere body 102 in equal directions. Each protrusion 104 may have aradial separation in the range of 10° for 45°. For example, a protrusion104 may be separated from an adjacent protrusion 112 by a radialdistance in the range of 10° for 45°. As will be appreciated, in someembodiments an increase in the diameter of the sphere body 102 mayinclude a decrease in the radial spacing of the protrusions 104, and adecrease in the diameter of the sphere body 102 may include an increasein the radial spacing of the protrusions 104.

The sphere 100 may define a protrusion length to sphere diameter ratio(referred to as “da/db” ratio). In some embodiments, the da/db ratio maybe in the range of 0.1 to 3.5. In some embodiments, the da/db ratio mayvary based on the particular application or deployment technique usedwith the LCM. For example, a greater da/db ratio may be used to enableformation of bridges from the spheres, such that additional LCMs may beintroduced into the lost circulation zone to form seals or plugs on thebridge. In another example, a lesser da/db ratio may be used to enableformation of plugs from the spheres without the use of another LCM.

In some embodiments, the diameter of the sphere 100 having theprotrusions 104 may be selected based on the deployment technique usedto deploy the LCM downhole to a lost circulation zone. In someembodiments, the LCM having the spheres 100 may be deployed through adrill bit; in such embodiments, the sphere 100 may have a diameter inthe range of 5 mm to 8 mm. In some embodiments, an LCM having thespheres 100 may be deployed using a bypass system (that is, a systemthat enables bypassing the BHA to introduce the LCM into the wellbore);in such embodiments, the sphere 100 may have a diameter in the range of9 mm to 14 mm. In some embodiments, an LCM having the spheres 100 may bedeployed using an open ended drill pipe; in such embodiments, the sphere100 may have a diameter in the range of 15 mm to 38 mm.

The sphere 100 may be formed from various materials that have thermalstability and resiliency. As used herein, the term “thermal stability”refers to stability of the material under downhole conditions (forexample, temperature and pressure) in a well such that the material doesnot degrade or dissolve. As used herein, the term “resiliency” refers toa material that is capable of elastic deformation. For example, theprotrusions 104 of the sphere 100 may be of sufficient resiliency sothat the protrusions 104 do not break off from the sphere body 102 whenthe sphere 100 impacts formation rock in a lost circulation zone.

FIG. 2 is a 2-D schematic diagram of a structure 200 (for example, abridge of plug) formed by the spheres 100 via contact betweenprotrusions 104 in accordance with an embodiment of the disclosure. Inshould be appreciated that although FIG. 2 is a 2-D depiction, thestructure 200 formed by the spheres 100 is a three-dimensional (3-D)structure. As shown in FIG. 2 each protrusion 104 may contact one ormore protrusions of an adjacent sphere when two sphere are in sufficientproximity to each other. For example, with regard to labeled spheres 202and 204, a protrusion 206 of sphere 202 may contact a protrusion 208 ofthe adjacent sphere 204. In this manner, each sphere 100 may engage anadjacent sphere to form the structure 200 via contact of theprotrusions. The contact between the protrusions 104 may result ininterlocking and entanglement of a sphere with one or more adjacentspheres. Each sphere may engage with one, two, three, four, five six ormore spheres to from the structure 200. Additionally, the spheres aroundthe edges of the structure 200 may be available for engagement withadditional spheres subsequently introduced into the lost circulationzone.

The structure 200 depicted in FIG. 2 may act as a bridge, a plug, orboth. For example, in some embodiments, the structure 200 may provide abridge for additional LCMs introduced into the lost circulation zone toform a seal or plug on the bridge. Additionally, or alternatively, thestructure 200 may form a plug that reduces or prevents lost circulationin a lost circulation zone without the use of additional LCMs. In someembodiments, the spheres used for formation of a bridge may have agreater da/db ratio than the spheres used for formation of a plug.

In some embodiments, the sphere 100 may be a nonmetallic material, suchas a polymer (for example, a plastic). In some embodiments, the sphere100 is formed from a non-swellable material, such that the spheres arenon-swellable in the presence of hydrocarbons or water. The materialforming the sphere 100 may have a rigidity sufficient to enable contactbetween a protrusions under downhole conditions (such as temperature andpressure) without deformation that prevents sufficient contact to enableengagement between adjacent spheres.

In some embodiments, the sphere 100 may be produced using additivemanufacturing (for example, 3-D printing). The sphere 100 may beproduced using known 3-D printing techniques, such as direct ink writing(DIW), inkjet printing fused deposited modeling, or stereolithography,or other techniques. The printable material (for example, an ink) mayinclude a nonmetallic composition having the thermal stability andresiliency mentioned in the disclosure.

In some embodiments, the sphere 100 may be produced using a mold to castshredded rubber and a binder into the sphere 100. In some embodiments,the shredded rubber is shredded rubber from scrap tires (for example,magnetically separated crumb rubber). In some embodiments, the binder ispolyurethane.

In some embodiments, the sphere 100 may be produced using a mold to casta heat-resistant plastic (for example, a thermosetting polymer) into thesphere 100. The sphere 100 may be produced using known plastic moldingtechniques, such as injection molding, or compression molding, ortransfer molding, or other techniques.

FIG. 3 depicts a process 300 for using the protrusion sphere LCM inaccordance with an embodiment of the disclosure. Initially, the size andda/db ratio of the spheres in the protrusion sphere LCM may be selected(block 302). As discussed in the disclosure, the size and da/db ratio ofthe spheres may be based on the type of lost circulation and thedeployment technique used to introduce the spheres into the lostcirculation zone.

In some embodiments, an LCM having a plurality of the spheres may beadded to carrier fluid to create an altered carrier fluid having theprotrusion sphere LCM for introduction into a lost circulation zone(block 304). For example, in some embodiments, the plurality of spheresmay be added directly to a drilling fluid, such as a drilling mud, tocreate an altered drilling fluid having the protrusion sphere LCM. Forexample, in some embodiments, the plurality of spheres may be added to(for example, mixed with) an oil-based drilling mud or a water-baseddrilling mud. In some embodiments, the protrusion sphere LCM may beadded at the mud pit of a mud system.

In some embodiments, the protrusion sphere LCM may have a concentrationin the range of 10 pounds-per-barrel (ppb) to 40 ppb in the carrierfluid. For example, at these concentrations, the carrier fluid may bepretreated to prevent or mitigate fluid loss. When loss circulation isencountered, the protrusion sphere LCM may have a concentration in therange from 40 ppb to 200 ppb. As will be appreciated, suchconcentrations may be dependent on the mechanism of introduction intothe lost circulation zone. For example, a concentration of about 40 ppbmay be a concentration limit of a motor or other BHA. In anotherexample, a concentration of about 200 ppb may be used with an open endeddrill pipe.

The altered carrier fluid may then be introduced into a lost circulationzone (block 306). After addition of the protrusion sphere LCM to acarrier fluid, the altered carrier fluid (for example, the altereddrilling fluid) may be circulated at a pump rate effective to positionthe carrier fluid into contact with a lost circulation zone in awellbore, such that the plurality of spheres alter the lost circulationzone (such as by forming a structure in paths, cracks, and fractures).In some embodiments, the protrusion sphere LCM may be introduced to thelost circulation zone through a drill bit. In some embodiments, theprotrusion sphere LCM may be introduced to the lost circulation zoneusing a bypass system. In some embodiments, the protrusion sphere LCMmay be introduced to the lost circulation zone using an open ended drillpipe.

In some embodiments, the protrusion sphere LCM may be used to form plugsin paths, cracks, and fractures in a formation in the lost circulationzone (block 308). In such embodiments, after introducing the protrusionsphere LCM into the lost circulation zone, drilling operations mayresume with a reduced rate of lost circulation of the drilling fluid.

In some embodiments, the protrusion sphere LCM may be used to formbridges in paths, cracks, and fractures in a formation in the lostcirculation zone (block 310). In such embodiments, an additional LCM maybe introduced into the lost circulation zone (block 312), such as via analtered drilling fluid having the additional LCM. The additional LCM mayaccumulate on the bridges formed by the protrusion sphere LCM to seal orplug the lost circulation zone. After introducing the additional LCMinto the lost circulation zone, drilling operations may resume with areduced rate of lost circulation of the drilling fluid.

Ranges may be expressed in the disclosure as from about one particularvalue, to about another particular value, or both. When such a range isexpressed, it is to be understood that another embodiment is from theone particular value, to the other particular value, or both, along withall combinations within said range.

Further modifications and alternative embodiments of various aspects ofthe disclosure will be apparent to those skilled in the art in view ofthis description. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the general manner of carrying out the embodiments described inthe disclosure. It is to be understood that the forms shown anddescribed in the disclosure are to be taken as examples of embodiments.Elements and materials may be substituted for those illustrated anddescribed in the disclosure, parts and processes may be reversed oromitted, and certain features may be utilized independently, all aswould be apparent to one skilled in the art after having the benefit ofthis description. Changes may be made in the elements described in thedisclosure without departing from the spirit and scope of the disclosureas described in the following claims. Headings used in the disclosureare for organizational purposes only and are not meant to be used tolimit the scope of the description.

1. A method to control lost circulation in a lost circulation zone in a wellbore, comprising: introducing an altered carrier fluid into the wellbore such that the altered carrier fluid contacts the lost circulation zone, wherein the altered carrier fluid comprises a carrier fluid and a lost circulation material (LCM), wherein the LCM comprises a plurality of spheres, each sphere comprising: a sphere body; and a plurality of substantially-straight protrusions, each protrusion extending outward from a surface of the sphere body; wherein a first protrusion of a sphere of the plurality of spheres is configured to contact a second protrusion of an adjacent sphere such that the plurality of spheres form a structure.
 2. The method of claim 1, wherein the LCM consists of the plurality of spheres.
 3. The method of claim 1, wherein the carrier fluid comprises an oil-based drilling mud or a water-based drilling mud.
 4. The method of claim 1, wherein the LCM comprises a first LCM, the method comprising: introducing an altered drilling fluid into the wellbore such that the altered drilling fluid contacts the lost circulation zone, wherein the altered drilling fluid comprises a drilling fluid and a second LCM, such that the second LCM accumulates on the structure.
 5. The method of claim 1, wherein each sphere of the plurality of spheres has a diameter in the range of 5 millimeter to 38 mm.
 6. The method of claim 1, wherein the sphere body has a diameter in the range of 3 millimeters to 34 mm.
 7. The method of claim 7, wherein each protrusion of the plurality of substantially-straight protrusions is separated from an adjacent protrusion by a radial distance in the range of 10° to 45°.
 8. The method of claim 1, wherein each protrusion of the plurality of substantially-straight protrusions has a length and the sphere body has a diameter, wherein the ratio of the length to the diameter is in the range of 0.1 to 3.5.
 9. The method of claim 1, wherein introducing the altered carrier fluid into the wellbore comprises pumping the altered carrier fluid through a drill bit.
 10. The method of claim 1, wherein introducing the altered carrier fluid into the wellbore comprises using a bypass system.
 11. The method of claim 1, wherein introducing the altered carrier fluid into the wellbore comprises introducing the altered carrier fluid into the wellbore using an open-ended drill pipe.
 12. A lost circulation material (LCM) composition, comprising: a plurality of spheres, each sphere comprising: a sphere body; and a plurality of substantially-straight protrusions, each protrusion extending outward from a surface of the sphere body; wherein a first protrusion of a sphere of the plurality of spheres is configured to contact a second protrusion of an adjacent sphere such that the plurality of spheres form a structure.
 13. The LCM composition of claim 12, wherein each sphere of the plurality of spheres has a diameter in the range of 5 millimeter to 38 mm.
 14. The LCM composition of claim 12, wherein the sphere body has a diameter in the range of 3 millimeters to 34 mm.
 15. The LCM composition of claim 12, wherein each protrusion of the plurality of substantially-straight protrusions is separated from an adjacent protrusion by a radial distance in the range of 10° to 45°.
 16. The LCM composition of claim 12, wherein each protrusion of the plurality of substantially-straight protrusions has a length and the sphere body has a diameter, wherein the ratio of the length to the diameter is in the range of 0.1 to 3.5.
 17. An altered drilling fluid, comprising: a drilling fluid; and a plurality of spheres, each sphere comprising: a sphere body; and a plurality of substantially-straight protrusions, each protrusion extending outward from a surface of the sphere body; wherein a first protrusion of a sphere of the plurality of spheres is configured to contact a second protrusion of an adjacent sphere such that the plurality of spheres form a structure.
 18. The altered drilling fluid of claim 17, wherein each sphere of the plurality of spheres has a diameter in the range of 5 millimeter to 38 mm.
 19. The altered drilling fluid of claim 17, wherein the sphere body has a diameter in the range of 3 millimeters to 34 mm.
 20. The altered drilling fluid of claim 17, wherein each protrusion of the plurality of substantially-straight protrusions is separated from an adjacent protrusion by a radial distance in the range of 10° to 45°.
 21. The altered drilling fluid of claim 17, wherein the drilling fluid comprises an oil-based drilling mud or a water-based drilling mud. 